Loading duplex or multiplex telephone-lines.



H. B. M. PLEHEL 6; A! H. ULSSQN.

LOADING DUPLEX 0R MUL TIPLEX TELEPHONE LINES. LED APR-27.1914- APPLICATION H 13, SHEE JGQZAJ by Dom dW W a Mf 2 W W e m WMJZ H. B. M. PLEH'EL & A. H. oLssow.

[OADJNG DUPLEX 0R MULHPLEX TELEPHONE LINES. APPLICATION FILED APR. 27. 1914.

2 SHEETS-SHEET 2.

Patented Feb. 13, 1917.

UNITED STES arena HENNING BERNHARD MATHIAS PLEIJEL AND AXEL HERMAN OLSSON, OF STOCKHOLM,

- SWEDEN.

LOADING DUPLEX OR MULTIPLEX TELEPHONE-LENES.

Specification of Letters Patent.

IPatented 13, l ffl.

Application filed April 27, 1914. Serial No. 834,864.

It; all whom it may concern:

Be it known that we, Hnwmxo Bnnxnano Marinas PLEIJEL and AXEL HERMAN OLS- son', subjects of the King of Sweden, residing at Stockholm, in the Kingdom of Sweden, have invented new and useful Improvements in Loading Duplex or Multiplex Telephone-Lines, of which the following is a specification.

By cluplicatable telephone lines is meant double lines which are combined in pairs in such a manner that, in addition to the two telephonic circuits which they themselves constitutethe so-called main lines-they supply a third so-called combination or du-.

plex line, the branches of which consisteach of one of the two main lines themselves connected in parallel. lVith'this arrangement oflines, 50% more telephonic circuits may be laid in one line than the double line actually contains. This is of great economic value, and therefore the practical pupinization of such lines is of great practical importance.

As is well known, ordinary double lines are most easily pupinized with the socalled double coils. These consist of two windings, each on one half of a ring-shaped core, and each in one branch conductor and so connected. that the two currents, flowing in contrary directions in the two branches, magnetize the core polelessly. In the combination line. however, the currents in the branches of each double line flow in the same direction. They would not therefore, in the case of such coils. magnetize the cores polelessly; but at the point where the half windings touch, lines of force would respectively enter and pass out of the core. This stray field is particula'ly harmful; for, as a result of' the necessarily close arrangement of the coils of all wires in one box. it will strike the "neighboring (YOllS and thereby give rise to cross-talk. In order to avoid this. magnetic screens might be placed around the coils. These would. however, possess the disadvantage that the eddy currents induced in them bythe stray field would considerably increase. the effective resistance of the com-. pound coils. The coils have therefore been wound in such a manner that each half winding is spread over the whole of the core. Thus, even if the direction of the current be the same in both branches. there is no stray field; but the. two half windings counteract each other and the coils possess no self-induction for the combination lines.

It has therefore been proposed, in addition to coils wound in this manner for the main lines, to connect additional similarly wound coils for the loading of the combination line; and this is done, either as described in the specification to the German Patent No. 209655. in which each main line possesses a separate set of coils for this purpose, or in the manner described in The Electrician, London. 1911, vol. 67 p. 771, in which the extra coils for the combination line are double coils, with four windings. which are connected with both main lines There is however the disadvantage common to both these proposals that even for circuits the self-induction of which they do not increase, the coils cause an increase in resistance. and thus decrease the pupii-iization." .liloreover. with combination line coils whcrein both main lines are conducted around a single core. it is exceedingly dillicult in practice to maintain sullicient independence of the three circuits. These disadvantages had however to be tolerated in orden to avoid the stray field before referred to.

lVith the aid of the present invention. it is possible to avoid all the disadvantages referred to by means of that very lield. By a suitable form of construction of the coilsi the stray fieldis so formed thatnt extends within the coil arrangement which therefore remains outwardly strayless in all. wt'irlting connections. This stray field, which isz-free from the disadvantages hitherto prevailing;

may then in the same coils which load the main lines. be employed forloading. the combination line. In this manner, rextra coils are not required. Moreover. each main line is independent while its duplicatability remains unaffected.

According to our improved method of arranging, tlie'coils. for each point of-loading, two of the above described well-known coils are taken; and these are connected inv series or in parallel, so that they hive the requisitemmount ot' self-induction at the point of connection. These two coils are then laid symmetrically one on the other, in such a manner that the divisions between the half windings which, when the stray tield is produced. has dissin'iilar 'iolarity,, cover each other. Thus. in the case of currents flowing in opposite directions in the branches ofthe other, as they produce in this case no ex- I ternal field. The arrangement acts in the same way as two ordinary compound coils connected in series or in parallel. In the case of currents flowing in the same direction, however, each coil absorbs the stray field of the other. What might be called internal stray field is however produced; and the compound coils, unlike those hitherto known, remain externally straylessin all working connections. This internal stray field can now be employed for the self-induction loading of the combination line.

In the accompanying drawing, Figures 1 and 2 show the' method of connecting a duplex line to the new coils. a combination of the coils present in Figs. 1 and 2', but on a larger scale. Fig. a shows a combination of coils connected in parallel. In Figs. 1 and 3, the-two coils are shown in 'the plane of the drawing displayed side by side with the object of making'the connections distinct. As a matter of fact the two coils which go together are placed, as described above and as shownin Fig. 2,"one on the other, and are connected by tapes or the like so as to form what externally resembles a single coil. As may be seen in Figs. 1 and 3, the.co1ls 1 and 2 of every combination are Wound 1n the same manner as the combination coils hitherto employed for ordinary duplex lines. The half windings are respectiyely on the halves of a ring-shaped magnetizing core and are separated by means of the disks A, B. Thedirections of the windings are so chosen that, in the case of a similar direction of the currents in both branches, for an instantaneous value of the current in (for instance) coil 1, a north pole is produced at A, a south pole at B, and in coil 2 a north pole at B and a south pole at A As A falls over A and B over B when Fig. 3 shows 1. Duplicate double tion of the current is the .same in. both branches of the double line, is surrounded in parallel by the two branches;

zation of the combination line.

In Figs. 1 and 3, the two coils of each com bination are shown in series connection. They may however be connected in parallel,

as already mentioned, and as illustrated in Fig. 4, without affecting the essence of the invention, it for instance it be deemed more advantageous as regards the attainment of the electrical efi'ects desired.-

The iron core may with advantage be being thereby rendered stronger and the self-induction of the combination line increased.

We claim I telephone lines worked on the Pupin system, loadedwith induction coils and wherein the'coils of the main lines consist of separate windings on separate It thereby produces theself-induction-for the pupiniiron cores laid together and so connected electrically that the phantom line becomes loaded by the stray fields created between the separate coils by the current in the phantom line.

'2. Duplicate double telephone lines worked on the Pupin system, and loaded with induc- .tion coils each of which consists of two double coils consisting of separate windings on,.separate iron cores laid together and so connected electrically that the magnetic poles created'by the current on the phantom line will be of opposite polarity at any one point in either pair of coils.

HENNING' BERNHARD MATHIAS PLEIJEL. AXEL HERMAN OLSSON.

Witnesses DAVID HEN UIST, ARvIs HOLMGREN.

Copies of this patent may be obtained for live cents each, by addressing the Commissioner of Patents,

Washington, D. C. 

